When developing new compounds for tires, a prior practice was to build a tire and subject the tire to various traction tests. Because of the cost and time needed to build test tires for the purpose of optimizing traction properties, small samples of tread compounds have instead been used to determine the traction characteristics of the compounds. By using small samples for testing, a large number of different tread compounds can be made in small batches for screening to determine which compound has the best properties. The small samples could also be tested with different friction test surfaces representing different road surfaces and different conditions, whereby the traction properties of the compounds may be observed to determine which compound has the best traction on a specific road surface under specific conditions.
In U.S. Pat. No. 5,113,688 there is disclosed an apparatus and method for predicting tire traction characteristics of tread compounds using small test samples. The apparatus causes a rotating relationship between the sample and friction surface. The peak torque between the sample and friction surface is measured and a torque versus time curve is established for the sample. Such apparatus, however, does not appear to be easily movable as may be desired for testing at different locations, nor is such apparatus suitable for evaluating the performance of different tread patterns. It would be advantageous to have a portable friction testing apparatus that not only can measure the coefficient of friction of plain tread elements, but also can measure the coefficient of friction of tread blocks, shoulders, etc., of existing tires. A further desirable advantage would be an apparatus that permits one to view the interaction between the friction surface and the specimen in the same way as the present invention.